Question

The images represent three samples of nitrogen dioxide, which is the pollutant responsible for the brown color of the atmospheric pollution. At high temperatures, nitrogen dioxide decomposes to nitrogen monoxide and oxygen gas.

Use the particulate model below to answer the following questions.

(b) (c) (a)

A plot of 1NO21NO2 versus time is linear. Using this information, identify the factor by which the rate will increase in model (c) if the number of molecules is increased by a factor of 2.

Answer 1

The plot of the change in concentration of NO₂ vs time is linear which means that the rate of change of NO₂ is first order in NO₂. Thus, the order of the reaction is 1 with respect to NO₂.

Consequently, when the concentration of NO₂ is doubled, the rate will double. Similarly, reducing the concentration of NO₂ to half its initial value will reduce the rate of the reaction to half the initial value. Since the number of molecules of NO₂ is increased by a factor of 2, i.e, there are 24 molecules of NO₂ in (a) instead of 12, the rate will increase by a factor of 2 and thus, there will be 6 molecules of NO₂ in (c).